Incandescent electric lamp.



R. WINNE.

INCANDE-SCENT ELECTRIC LAMP.

APPLICATION man APR. 24. 1913.

1 1 97,705 Patented Sept. 12,1916.-

Witnesses: Inventor j Rog Winne,

y MM UNITED STATES PATENT OFFICE.

ROY WINNE, OF SCHENECTADY, YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

I INGANDESCENT ELECTRIC LAMP.

The present invention relates to incandescent lamps, and especially to lamps provided with a metal filament, particularly a tungsten filament.

It is one of the objects of my invention to increase the useful life of such lamps and also to maintain the efiiciency atwhich the filament is operating substantially constant at a high value.

When a tungsten filament is operated'in an evacuated bulb under ordinary conditions, the resistance of the filament grad- I uall'y. increases, thus lowering its temperature, and the bulb is progressively darkened by a black deposit of vaporized tungsten. Both these effects contribute to loweringthe efiiciency and candle power of the lamp.

When the eiiiciency has been reduced to a certain value, say 80%, the lamp has reached tlfe end of its useful life.

In order to increase the length of life of a lamp at a given efiiciency various solid halogenous compounds of low vapor tension, such as potassium thallium chlorid, cryolite, or potassium iodid have been placed in the lamp. These compounds are placed in the lamp in such a position that when the filament is at normal incandescence and the bulb'is well evacuated there is evolved an atmosphere which is chemically active to the metal of the filament and which is of substantially the pressure of a first class vacuum,

Specification of Letters Patent.

Patented Sept. 12, 1916.

Application filed April 24, 1913. Serial No. 763,263.

mounted upon a support 3 and is connected 1 to leading-in conductors 4, 5, which are sealed into the stem 6 and connected as usual to the base contacts 7 and 8. The lamp is.

340 360? C. while completing the exhaustion on the fine pump. The temperature is then lowered to about 25027 0 C. and about of the normal lamp voltage is impressed upon the filament. The lamp is run in this way until the vacuum becomes as.

good as about '2 microns. The heating and current are then discontinued and about 100 microns of dry nitrogen admittedf The filament is incandesced for about 10' seconds and the gas pumped out again to about 2 microns pressure. More dry nitrogen to the desired pressure is admitted and the bulb is then sealed off. Ordinarily the pres-' sure of the gaseous atmosphere should be less than 100 microns, and usually within the range of about 10 to 50 microns, or .010 to .050 millimeter of mercury. A gas pressure as great as 100 microns is apt to produce destructive electrical discharges between the leads at commercial voltages, such as 110 volts or higher. Of course, this particular procedure may be varied considerably in accordance with the character of the lamp'and other conditions.

To illustrate the effect of my novel filling combination on the life of the lamp, I desire briefly to cite several specific examples. A 125 volt, 100 watt lamp, having a drawn tungsten filament was provided with a small amount of potassium thallium chlorid placed in the same way as in a vacuum lamp. The bulb was evacuated as above described and then enough dry nitrogen gas was admitted to produce an atmosphereof about 25 microns (0.025 mm... of mercury) pressure. The lamp was then sealed oil and operated at an efficiency of .95 watt per candle. After 1900 hours, the candle power had fallen only to 96% of its original value. During the operation of the lamp the resistance of the filament repeatedly increased several per cent. and-then came back to normal. In the absence of the nitrogen the efiiciencyof a lamp of this type containing potassium thallium chlorid would have fallen to about 80% in about 1000-1200 hours. A similar lamp provided in the same manner with potassium thallium chlorid and nitrogen was found after operating 1000 hours at ..95 watt per candle to have actually increased in eflicien-"y, as it Wasoperating at 101% of its original candle power.

\Vhile I prefer to use nitrogen gas, I find that a small amount of air, carbon dioxid, oxygen. and even hydrogen may be similarly used although with less beneficial efi'ect in the order mentioned.

lVhile the benefits of my invention may be secured irrespective of any theory, it may be said that the following reactions perhaps take place. lVhen nitrogen is used, for example, tungsten vaporized by the incandes cence of the filament is probably converted into tungsten nitrid. This would soon exhaust the supply of nitrogen but .the nitrid is decomposed by the halogen compound to regenerate nitrogen. The tungsten compound on its part is decomposed at the temperature of the filament, depositing tungsten on the surface of the filament. I do not wish to be limited, however, by this theory of the behavior of the lamp.

\Vhat I claim as new and desire to secure by Letters Patent of the United States, is

1. An incandescent lamp comprising an envelop, a metal filament therein, a solid halogenous compound placed therein to evolve when said filament is at normal incandescence in a first class vacuum a va or chemically active tothe material of the ament and at substantially the pressure of a first class vacuum, and a charge of gas hava millimeter of mercury.

2. In an incandescent lamp, the combinament therein, and potassium thallium ch1o rld placed in said envelop to evolve in'the evacuated envelop at normal incandes'cence tion with an envelop having a tungsten filaof the filament an atmosphere of vapor at substantially the pressure of a first class vacuum, of nitrogengas in said envelop at a pressure of about .0l0.050 millimeter'of mercury pressure. I

3. An incandescent lamp comprising an envelop containing a tungsten filament, a solid halogenous compound which evolves at normal incandescence of the filament when said envelop is evacuated to a first class vacuum an atmosphere of vapor chemically active to tungsten and of a pressure substantially that of a first class vacuum, and a charge of nitrogen having an initial pressure less than one tenth of a millimeter of mercury.

4. An incandescent lamp comprising an. envelop, containing a tungsten filament, a solid halogenous compound which evolves at normal incandescence of the filament when R Y WINNE. Witnesses:

BENJAMIN B. HULL,

- HELEN Onronn. 

